In a large skillet over medium-high heat, heat the vegetable oil. Cook and stir onion, red bell pepper, and green bell pepper in the hot oil, stirring frequently, until onion is translucent and peppers are soft, 6 to 8 minutes.
Stir salt, cumin, and chili powder into onion and bell peppers.
Stir shrimp into onion and bell peppers and cook until shrimp are opaque and no longer pink in the center, 3 to 5 minutes.
Remove skillet from heat; stir jalapeño pepper and lime juice into shrimp mixture.
Heat a skillet over medium heat and brush with about 1 teaspoon vegetable oil.
Place a tortilla in the hot oil. Spoon about 1/6 of the shrimp filling and 1/2 cup cotija on one side of tortilla. Fold tortilla in half.
Cook until bottom of tortilla is lightly browned, about 5 minutes; turn over and cook other side until lightly browned, 3 to 5 minutes. Repeat with remaining tortillas and filling.